Enables the use of some features on reedline
- Keeping the line when clearing the screen with `Ctrl-L`
- Using the internal cut buffer between lines
- Submitting external commands via keybinding and keeping the line
Additional effect:
Keep the history around and do basic syncs (performance improvement
minimal as session changes have to be read and written)
Additional change:
Give the option to defer writing/rereading the history file to the
closing of the session ($config.sync_history_on_enter)
0986c61a5d